A liquid ‘P’ is 13times as heavy as water is 712 times

A liquid ‘P’ is 1 3 times as heavy as water is
7
1 2 times as heavy as another liquid ‘Q’.
5
The amount of liquid ‘P’ that must be added to 7 litres of the liquid ‘Q’ so that the mixture may weigh as much as an equal volume of water, will be

Let x litres of liquid P be mixed
to 7 litres of liquid Q.
According to the question,

x ×	10	+	5	× 7 = x + 7
	7		7

⇒	10x	+ 5 = x + 7
	7

⇒ 10x + 35 = 7x + 49
⇒ 10x – 7x = 49 – 35
⇒ 3x = 14

⇒ x =	14	= 4	2	litres
	3		3